Laryngeal air cyst, also known as laryngeal bulge, laryngeal diverticulum or laryngeal air hernia, is an abnormal expansion of the laryngeal ventricular sac, containing gas. The laryngeal ventricular sac of infants and young children is relatively large, generally 6-8mm, and a few can be as large as 10-15mm. Those with very large sacs are called congenital laryngeal air cysts. The formation of laryngeal air cysts in adults is mostly caused by congenital abnormalities of the laryngeal ventricular sacs, coupled with chronic coughing, trumpeting, weightlifting, laryngeal tumors, etc., which increase the pressure and expand the laryngeal ventricular sacs. According to the location of the air cyst, it is divided into three types: intra-laryngeal, extra-laryngeal, and mixed intra-laryngeal and extra-laryngeal. The air cyst located in the larynx is the intra-laryngeal type. There are two types of this type. One protrudes from the laryngeal ventricle, pushes the laryngeal ventricular belt upward, covers the ipsilateral vocal cord, and even extends to the opposite side, obstructing the glottis; the other protrudes from the aryepiglottic folds, deforming the ipsilateral larynx, and some even extend upward to the root of the tongue, located in the epiglottic valley. The air cyst appears in the neck is the extra-laryngeal type. This type of cyst often pierces the superior laryngeal nerve and blood vessels of the thyrohyoid membrane and is located at the front edge of the sternocleidomastoid muscle under the hyoid bone; it can also pierce the cricothyroid membrane and be located below the thyroid cartilage. The mixed type is a cyst that appears in the larynx and neck at the same time, connected by an isthmus at the thyrohyoid membrane.